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| author | Miklos Szeredi <mszeredi@redhat.com> | 2020-06-04 10:48:19 +0200 |
|---|---|---|
| committer | Miklos Szeredi <mszeredi@redhat.com> | 2020-06-04 10:48:19 +0200 |
| commit | df820f8de4e481222b17f9bcee7b909ae8167529 (patch) | |
| tree | 8410725a7cd85f540f59120710b8617c18348670 /fs/overlayfs | |
| parent | b8e42a651bdee06202ebdd96cff64fdeabd5b1d6 (diff) | |
| download | lwn-df820f8de4e481222b17f9bcee7b909ae8167529.tar.gz lwn-df820f8de4e481222b17f9bcee7b909ae8167529.zip | |
ovl: make private mounts longterm
Overlayfs is using clone_private_mount() to create internal mounts for
underlying layers. These are used for operations requiring a path, such as
dentry_open().
Since these private mounts are not in any namespace they are treated as
short term, "detached" mounts and mntput() involves taking the global
mount_lock, which can result in serious cacheline pingpong.
Make these private mounts longterm instead, which trade the penalty on
mntput() for a slightly longer shutdown time due to an added RCU grace
period when putting these mounts.
Introduce a new helper kern_unmount_many() that can take care of multiple
longterm mounts with a single RCU grace period.
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/super.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index eb81d8760a6a..8d8cd46e1482 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -211,6 +211,7 @@ static void ovl_destroy_inode(struct inode *inode) static void ovl_free_fs(struct ovl_fs *ofs) { + struct vfsmount **mounts; unsigned i; iput(ofs->workbasedir_trap); @@ -224,10 +225,14 @@ static void ovl_free_fs(struct ovl_fs *ofs) dput(ofs->workbasedir); if (ofs->upperdir_locked) ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root); + + /* Hack! Reuse ofs->layers as a vfsmount array before freeing it */ + mounts = (struct vfsmount **) ofs->layers; for (i = 0; i < ofs->numlayer; i++) { iput(ofs->layers[i].trap); - mntput(ofs->layers[i].mnt); + mounts[i] = ofs->layers[i].mnt; } + kern_unmount_array(mounts, ofs->numlayer); kfree(ofs->layers); for (i = 0; i < ofs->numfs; i++) free_anon_bdev(ofs->fs[i].pseudo_dev); |